1. Field of the Invention
The present invention relates to auxiliary welding equipment and particulary to apparatus for removing flash from the inside surface of the weld-joined pipes. Most successfully the invention can be used in laying trunk pipelines as well as in welding casing pipes.
The apparatus for removing flash from the inside surface of the pipes have been used for a comparatively long time. Despite this fact, however, the above apparatus are short-lived and unreliable in operation. Besides, weld-joined pipes are often damaged in the course of removing flash with the aid of such apparatus. The present invention has as its aim to solve this problem and to overcome the above disadvantages.
2. Description of the Prior Art
Known in the art is an apparatus for removing flash (see USSR Inventor's Certificate No. 212,192), comprising a body with a circular cutting tool rigidly attached thereto. The diameter of the cutting tool is somewhat smaller than the inner diameter of the pipe, which enables the apparatus to freely enter the pipe. The body of the apparatus bears up against the inside surface of the pipe through the intermediary of rollers. The cutting edge of the tool is disposed around the periphery thereof. The apparatus removes flash all at once along the whole of the annular weld between the weld-joined pipes.
The above-described apparatus can be used only in those cases when pipes have a diameter of not more than 400 mm and a rigidity sufficiently high to preclude the possibility of any deformation or eccentricity. For welding pipes of a large diameter (more than 700 mm) this apparatus is not fit for use, because in this case ellipticity of the pipes (even under the action of their own weight) and local deformation of their walls (such as dents) are inevitable. Being of a constant diameter, the tool is sure to damage the pipe even before it comes in contact with flash.
More promising in this respect is an apparatus for removing flash from the inside surface of weld-joined pipes, as described in USSR Inventor's Certificate No. 468,730. This apparatus comprises a body and radially movable cutting tool holders disposed around the periphery thereof. The cutting tool holders have supporting members made in the form of protrusions contacting the inside surface of the pipe. Said protrusions are provided only on the front ends of the cutting tool holders. Through its rear end each cutting tool holder is pivoted to the body. Cutting tools are rigidly attached to the cutting tool holders. The apparatus is also provided with springs for pressing the cutting tool holders against the inside surface of the pipe. Although the cutting tool holders are constantly pressed against the inside surface of the pipe, the cutting tools are prevented from cutting into the wall of the pipe when the apparatus moves within the latter by the supporting protrusions which follow the configuration of the inside surface of the pipe and, in conjunction with the springs, turn the cutting tool holder, maintaining a constant space between the cutting tools and the pipe. At the same time the supporting protrusions do not prevent the cutting tool from cutting flash. The flash is a narrow bead; therefore the protrusion passes over it and lowers again, thus permitting the cutting tool to cut the flash.
However, alongside with the advantages, the apparatus under consideration also suffers from some essential drawbacks. In particular, to enable the movement of the apparatus within the pipe, an appreciable force is required to overcome the friction between the protrusions of the cutting tool holders and the pipe walls. In addition, the contacting surfaces of the cutting tool holders wear out rapidly, which is accompanied by an increase in the depth of cutting and may cause either a breakdown of the cutting tools, or a damage of the weld. For this reason, such apparatus need frequent maintenance, and the welds should be thoroughly detected for cracks after the flash has been removed therefrom.